Most portable electrical devices use batteries to supply power to the device. When a charge in the battery is depleted, the battery must be replaced. With most electrical devices, battery replacement is not problematic. With emergency electrical devices, however, the time required to replace a battery can at times be unacceptable. For example, emergency medical devices such as portable defibrillators use one battery as the power source. When the battery is depleted, the operator must manually remove the battery and install a fresh one. In a clinical setting, this manual method of exchanging batteries may result in delay of critically needed medical treatment. Additionally, if a replacement battery is unavailable, the emergency electrical device may fail of its essential purpose.
Some emergency electrical devices use two or more batteries. A manually actuatable switch allows the operator to switch from a depleted battery to a fresh one. This manual method can delay critically needed medical treatment. Diodes or other hardware devices have been used to automatically select the battery with a greater charge to power the electrical device. After the battery with the greater charge is partially depleted, the second battery then has a greater charge and is used to power the electrical device. This process of swapping between batteries as they alternatively obtain a greater charge than the other continues until both batteries are depleted. Half depleted batteries are not as reliable as more fully charged batteries. By slowly draining both batteries, the electrical device therefore becomes less reliable. Additionally, if one of the two partially drained batteries fails, the other battery may quickly be depleted, requiring the operator to replace new batteries into the system. The reason for providing two or more batteries to avoid replacement during critical times is defeated. The operator must also remember to constantly carry additional fresh batteries.
Most portable electrical devices use a rechargeable battery to power the device. When a charge in the battery is depleted, the battery is removed from the device and connected to a charging circuit which recharges the battery by pumping current into the battery. Some rechargeable batteries are damaged when they are frequently recharged or they are recharged when they are not depleted. Consequently, an operator of the device could possibly wait until the battery is fully depleted before recharging it. With emergency electronic devices, this practice is often unacceptable because the operator may need to replace the battery during a critical period.
Some emergency electronic devices have a battery status indicator to notify the operator of the battery's status. The drain on a battery can vary greatly from moment to moment while the device is actively being used. The operator, therefore, must frequently monitor the status of the batteries and again carry additional fully charged batteries at all times. Furthermore, battery status may change erratically while the device is actively being used. Consequently, any indication of the batteries' status could be erroneous.
Rechargeable batteries lose their charge faster after being recharged as compared to nonrechargeable batteries. Consequently, the batteries should be used soon after being recharged. The operator must insure that any spare batteries he or she carries are not old. During an emergency situation, the operator may forget to carry freshly charged batteries or forget to bring additional batteries altogether. The operator may also forget to recharge the batteries after an emergency. As a result, the next time the emergency electronic device must be used, the batteries may not be fully charged and therefore may run out of power during a critical period. Furthermore, rechargeable batteries require the operator to diligently recharge the battery when it is depleted. The above host of problems inherent in rechargeable batteries can result in an unreliable electronic device or result in delays, both being unacceptable for emergency electrical devices.
It often requires over 12 hours to fully recharge a rechargeable battery. Operators generally would prefer a faster battery charging circuit. Such circuits have been developed which provide high and low charges to a battery. The high charge is first applied to the battery to recharge the battery up to 80% of its capacity. Thereafter, the low charge is applied to the battery to fully charge it. Some of these high/low chargers accept more than one battery and subject all batteries to the high charge, and then to the low charge. The operator must wait until all the batteries placed in the charging device are recharged before connecting them back to the electronic device. Therefore, when these chargers are used in conjunction with emergency electronic devices, many batteries must be purchased and recharged so that, in addition to the batteries in the device, some fully charged batteries are on hand in the event of an emergency, while other batteries are being recharged. The additional batteries are an added expense.
Overall, the inventors are unaware of a reliable portable electronic device using two or more rechargeable batteries which provide continuous power to the device, without any delays, and which charges the batteries without relying on the operator's memory or diligence in carrying additional batteries or recharging depleted ones.